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The Powermeter Thread

Moderator: King Boonen

04 Mar 2013 17:43

JayKosta wrote:Coach Fergie,

When designing your project, I suggest that you be very careful and critical to avoid 'problem areas' such as were discussed regarding the Burns article.

For example -

The length / intensity / frequency of the training period needs to be adequate to produce results that are measureable.

If the testers are told/requested to DO something, then there should be some method to objectively verify that it was done, and how well it was done.

If the testers are being taught a 'new technique', then there should be some testing to determine what is their 'current technique'. So that before-after comparisons are meaningful.

I don't know what you have in mind to study, but I would like to see a study that compares training by -
1) power meter
2) heart rate
3) perceived exertion

Jay Kosta
Endwell NY USA
Perhaps Fergie will post his ideas for a study here for critical review by the group before he finalizes his proposal. Fergie is about to find out how difficult it is to design and complete a well-designed study on a subject such as this. I wonder if his own study shows no benefit to a power meter (and no other study has yet to show a benefit) if he will change his recommendations to his athletes and everyone else? This should be interesting.
Life is short, both reading my posts and training with PowerCranks will make it seem longer
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04 Mar 2013 17:49

veganrob wrote:Fergie,
Thanks for starting a thread that can answer some Power Meter questions. I have a PowerTap hub and my cranks are Rotor 3D+ with Q rings. I have been riding them for three years and like them. I have no proof that they have increased my power at all but like the feel of them from the first time I rode them. My question is calibration, would this be done differently because of the Q rings. thanks


You can check the calibration of a Powertap but you can't change the calibration of one.

Any engineers care to comment about hanging a known weight off a crank with a Q ring to check the calibration of a Powertap.
Hamish Ferguson
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04 Mar 2013 18:01

FrankDay wrote:Perhaps Fergie will post his ideas for a study here for critical review by the group before he finalizes his proposal. Fergie is about to find out how difficult it is to design and complete a well-designed study on a subject such as this. I wonder if his own study shows no benefit to a power meter (and no other study has yet to show a benefit) if he will change his recommendations to his athletes and everyone else? This should be interesting.


I already know how hard it is to design a study and currently the hurdles involved at the Ethics approval stage.

Frank, you still try and create a strawman by suggesting that a Power Meter should provide a benefit. A set of scales provides no benefit to the weight loss process only tells you if it is actually happening. A heart rate monitor doesn't tell you if you are fitter or not not (heart rate for a given effort can go down as you become more efficient but can also rise as you learn to tolerate a higher intensity for that duration.

I don't expect my new SRM (well second hand as I don't consider myself worthy of the latest model) to benefit my performance one bit. I do expect it to measure watts.

I performed a test of various shoes using a Powertap and initially found a difference in one brand that you would have expected but when I tested in reverse order found the opposite. I assume the difference was in the heat of the roller on the wind trainer I used. When I tested again with the SRM the difference I found was minimal and well within the margin of error you would expect in that model of SRM.

If I was being funded to perform the tests I would use the erg at the local Uni that has a higher sampling rate and a lower margin of error.
Hamish Ferguson
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04 Mar 2013 18:03

CoachFergie wrote:You can check the calibration of a Powertap but you can't change the calibration of one.

Any engineers care to comment about hanging a known weight off a crank with a Q ring to check the calibration of a Powertap.
Just as the calibration of the powertap doesn't change with the size of the wheel or whether the bike is in the small or large chain ring the fact that one has a non-round chain ring has no effect on the calibration or accuracy of the powertap.
Life is short, both reading my posts and training with PowerCranks will make it seem longer
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04 Mar 2013 18:16

JayKosta wrote:When designing your project, I suggest that you be very careful and critical to avoid 'problem areas' such as were discussed regarding the Burns article.

For example -

The length / intensity / frequency of the training period needs to be adequate to produce results that are measureable.

If the testers are told/requested to DO something, then there should be some method to objectively verify that it was done, and how well it was done.

If the testers are being taught a 'new technique', then there should be some testing to determine what is their 'current technique'. So that before-after comparisons are meaningful.

I don't know what you have in mind to study, but I would like to see a study that compares training by -
1) power meter
2) heart rate
3) perceived exertion


Thanks for your interest Jay

My study is a methodological one looking to see if a power meter offer a reliable way of tracking changes in cycling specific fitness over time based on racing and training data compared to power meter data from a lab based test.

I am open to suggestions of doing a study that does compare those three variables but how would you get beyond the issues of the Swart and Robinson papers where each group essentially performs the same training. No surprise that there was no significant change in performance in the heart rate and power meter groups.

One question I would like to test is whether a power meter improves pacing of events like the 40km TT. I have some riders who sit on a power number while others prefer to go by feel. Then it would also depend on the course and the weather conditions for any given day.
Hamish Ferguson
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04 Mar 2013 18:18

CoachFergie wrote:I already know how hard it is to design a study and currently the hurdles involved at the Ethics approval stage.

Frank, you still try and create a strawman by suggesting that a Power Meter should provide a benefit. A set of scales provides no benefit to the weight loss process only tells you if it is actually happening. A heart rate monitor doesn't tell you if you are fitter or not not (heart rate for a given effort can go down as you become more efficient but can also rise as you learn to tolerate a higher intensity for that duration.

I don't expect my new SRM (well second hand as I don't consider myself worthy of the latest model) to benefit my performance one bit. I do expect it to measure watts.

I performed a test of various shoes using a Powertap and initially found a difference in one brand that you would have expected but when I tested in reverse order found the opposite. I assume the difference was in the heat of the roller on the wind trainer I used. When I tested again with the SRM the difference I found was minimal and well within the margin of error you would expect in that model of SRM.

If I was being funded to perform the tests I would use the erg at the local Uni that has a higher sampling rate and a lower margin of error.

I am not trying to create any strawman. It just so happens that many people purchase a power meter because they believe that it will help them to improve beyond what they can do without it.

Anyhow, since this is a science thread and since you have said all this perhaps you could tell us then exactly what hypothesis regarding the power meter you hope to test in your study.
Life is short, both reading my posts and training with PowerCranks will make it seem longer
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04 Mar 2013 19:26

FrankDay wrote:I am not trying to create any strawman. It just so happens that many people purchase a power meter because they believe that it will help them to improve beyond what they can do without it.


Yes and I went twice as fast on yesterday's ride because I had two power meters on.

Anyhow, since this is a science thread and since you have said all this perhaps you could tell us then exactly what hypothesis regarding the power meter you hope to test in your study.


I started the thread and it's a power meter thread.

It's a methodological study to test if a power meter measuring wattage from racing and training is a valid and reliable way of tracking cycling specific fitness.
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04 Mar 2013 19:40

CoachFergie wrote:It's a methodological study to test if a power meter measuring wattage from racing and training is a valid and reliable way of tracking cycling specific fitness.
???

What is your gold standard by which you will compare to determine validity and reliability? Again, what is your hypothesis?
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04 Mar 2013 19:41

Ergometer Error and Biological Variation
in Power Output in a Performance Test with
Three Cycle Ergometers

C. D. Paton1
W. G. Hopkins2

Abstract
When physical performance is monitored with an ergometer,
random error arising from the ergometer combines with biological
variation from the subject to limit the precision of estimation
of performance changes.We report here the contributions of ergometer
error and biological variation to the error of measurement
in a performance test with two popular cycle ergometers
(air-braked Kingcycle, mobile SRM crankset) and a relatively
new inexpensive mobile ergometer (PowerTap hub). Eleven
well-trained male cyclists performed a familiarization trial followed
by three 5-min time trials within 2wk on a racing cycle
fitted with the SRM and PowerTap and mounted on the Kingcycle.
Mean power output in each trial was recorded with all ergometers
simultaneously. A novel analysis using mixed modelling
of log-transformed mean power provided estimates of the
standard error of measurement as a coefficient of variation and
its components arising from the ergometer and the cyclists. The
usual errors of measurement were: Kingcycle 2.2%, PowerTap
1.5%, and SRM 1.6% (90% confidence limits ± 1.3). The components
of these errors arising purely from the ergometers and the
cyclists were: Kingcycle 1.8%, PowerTap 0.9%, SRM 1.1%, and cyclists
1.2% (± 1.5). Thus, ergometer errors and biological variation
made substantial contributions to the usual error of measurement.
Use of the best ergometers and of test protocols that reduce
biological variation would improve monitoring of the small
changes that matter to elite athletes.
Key words
Reliability · mobile ergometer · kingcycle · powertap · SRM
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04 Mar 2013 19:47

A comparison of cycling SRM crank and strain gauge
instrumented pedal measures of peak torque, crank angle at
peak torque and power output

Rodrigo R. Bini, Patria A. Hume, Andre Cerviri

Procedia Engineering 13 (2011) 56–61

Abstract
Our aim was to compare an SRM® torque analysis system with a strain gauge instrumented pedals system for right
and left peak crank torque, crank angle of peak torque and power output. Seven competitive cyclists performed an
incremental test to exhaustion on a stationary cycle ergometer equipped with an SRM® torque analysis system and a
strain gauge instrumented pedals system (SGI pedals). The SRM® torque analysis system measured net torque while
the SGI pedals measured the normal and anterior-posterior force applied on the pedal surface. Forces on the pedal
surface were resolved into forces on the cranks (tangential and radial). Crank torque was measured by the pedals
using the tangential force on the cranks and crank length. Power output was calculated from crank torque and angular
velocity of the crank (calculated from pedalling cadence). All data were acquired between the 20th and the 40th
seconds of each stage of the incremental test. Magnitudes of differences between outputs from the SGI pedals and the
SRM® torque analysis system were assessed by effect sizes. Power output was higher for the SRM® torque analysis
system than the SGI pedals. Peak torques were lower for the SRM® torque analysis system compared to the SGI
pedals. The angle of the right and left peak torque increased for the SRM® torque analysis system compared to the
SGI pedals. The SRM® torque analysis system overestimated power output, underestimated peak torque and increased
the angle of peak torque compared to the SGI pedals. Where possible a strain gauge instrumented pedals system
should be used to measure performance variables of cyclists rather than the SRM® torque analysis system.
Hamish Ferguson
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04 Mar 2013 20:01

Mechanically braked Wingate powers: agreement
between SRM, corrected and conventional methods of
measurement

JAMES BALMER, STEVE R. BIRD, R.C. RICHARD DAVISON,
MIKE DOHERTY AND PAUL M. SMITH

In this study, we assessed the agreement between the powers recorded during a 30 s upper-body Wingate test
using three different methods. Fifty-six men completed a single test on a Monark 814E mechanically braked
ergometer fitted with a Schoberer Rad Messtechnik (SRM) powermeter. A commercial software package
(Wingate test kit version 2.21, Cranlea, UK) was used to calculate conventional and corrected (with accelerative
forces) values of power based on a resistive load (5% body mass) and flywheel velocity. The SRM calculated
powers based on torque (measured at the crank arm) and crank rate. Values for peak 1 and 5 s power and mean
30 s power were measured. No significant differences (P40.05) were found between the three methods for 30 s
power values. However, the corrected values for peak 1 and 5 s power were 36 and 23% higher (P50.05)
respectively than those for the conventional method, and 27 and 16% higher (P50.05) respectively than those
for the SRM method. The conventional and SRM values for peak 1 and 5 s power were similar (P40.05).
Power values recorded using each method were influenced by sample time (P50.05). Our results suggest that
these three measures of power are similar when sampled over 30 s, but discrepancies occur when the sample
time is reduced to either 1 or 5 s.
Keywords: arm cranking, maximal intensity exercise.
Hamish Ferguson
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04 Mar 2013 20:19

Validity and Reproducibility of the
Ergomo®Pro Power Meter Compared With
the SRM and Powertap Power Meters

Sébastien Duc, Vincent Villerius, William Bertucci,
and Frédéric Grappe

Purpose: The Ergomo®Pro (EP) is a power meter that measures power output
(PO) during outdoor and indoor cycling via 2 optoelectronic sensors located in
the bottom bracket axis. The aim of this study was to determine the validity and
the reproducibility of the EP compared with the SRM crank set and Powertap
hub (PT). Method: The validity of the EP was tested in the laboratory during
8 submaximal incremental tests (PO: 100 to 400 W), eight 30-min submaximal
constant-power tests (PO = 180 W), and 8 sprint tests (PO > 750 W) and in the
field during 8 training sessions (time: 181 ± 73 min; PO: ~140 to 150 W). The
reproducibility was assessed by calculating the coefficient of PO variation (CV)
during the submaximal incremental and constant tests. Results: The EP provided a
significantly higher PO than the SRM and PT during the submaximal incremental
test: The mean PO differences were +6.3% ± 2.5% and +11.1% ± 2.1%, respectively.
The difference was greater during field training sessions (+12.0% ± 5.7%
and +16.5% ± 5.9%) but lower during sprint tests (+1.6% ± 2.5% and +3.2% ±
2.7%). The reproducibility of the EP is lower than those of the SRM and PT (CV
= 4.1% ± 1.8%, 1.9% ± 0.4%, and 2.1% ± 0.8%, respectively). Conclusions: The
EP power meter appears less valid and reliable than the SRM and PT systems.

Key Words: cycling, mobile power meter, comparison, field, laboratory
Hamish Ferguson
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04 Mar 2013 20:26

Validity and reliability of the Axiom PowerTrain cycle ergometer when compared with an SRM powermeter.

Bertucci W, Duc S, Villerius V, Grappe F.

Int J Sports Med. 2005 Jan-Feb;26(1):59-65.

Abstract
The purpose of this study was to determine the validity and the reliability of a stationary electromagnetically-braked cycle ergometer (Axiom PowerTrain) against the SRM power measuring crankset. Nineteen male competitive cyclists completed four tests on their bicycle equipped with a 20-strain gauges SRM crankset: a maximal aerobic power (MAP) test and three 10-min time trials (TTs) with three different simulated slopes (0, 3, and 6 %). The Axiom ergometer overestimated (p <0.05) the SRM power output during the last stage of the MAP test and during TTs, by 5 % and 12 %, respectively. Power output (PO) of the Axiom ergometer drifted significantly (p <0.05) with the time during TT. These findings indicate that the Axiom ergometer does not provide a valid measure of PO compared with SRM. However, the small coefficient of variation (2.2 %) during the MAP test indicates that the Axiom provides a reliable PO and that it can be used e.g. for relative PO comparisons with competitive cyclists during a race season.
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04 Mar 2013 20:27

Also just like to suggest that where possible that people try and find the full paper if interested in this topic or any topic...

http://evidencebasedfitness.blogspot.co.nz/2013/03/hey-eff-tard-with-abstract-link-yeah-you.html
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04 Mar 2013 20:35

The Validity of Power Output Recorded During Exercise
Performance Tests Using a Kingcycle Air-Braked Cycle Ergometer
When Compared With an SRM Powermeter

J. Balmer, R. C. R. Davison, D. A. Coleman, S. R. Bird

This study assessed the validity of power output recorded
using an air-braked cycle ergometer (Kingcycle™) when compared
with a power measuring crankset (SRM™). For part one
of the study thirteen physically active subjects completed a continuous
incremental exercise test (OBLA), for part two of the
study twelve trained cyclists completed two tests; a maximal
aerobic power test (MAP) and a 16.1 km time-trial (16.1 km TT).
The following were compared; the peak power output (PPO) recorded
for 1 min during MAP, the average power output for the
duration of the time-trial and power output recorded during
each stage of OBLA. For all tests, power output recorded using
Kingcycle was significantly higher than SRM (P < 0.001). Ratio
limits of agreement between SRM and Kingcycle for OBLA
showed a bias (P < 0.00) of 0.90 (95%CI = 0.90–0.91) with a random
error of ×/÷ 1.07, and for PPO and 16.1 km TT ratio limits of
agreement were 0.90 (95%CI = 0.88–0.92) ×/÷ 1.07 and 0.92
(95%CI = 0.90–0.94) ×/÷ 1.07, respectively. This data revealed
that the Kingcycle ergometry system did not provide a valid
measure of power output when compared with SRM.
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04 Mar 2013 21:30

Agreement between polar and SRM mobile ergometer systems during laboratory-based high-intensity, intermittent cycling activity.

Hurst HT, Atkins S.

J Sports Sci. 2006 Aug;24(8):863-8.

Abstract
The purpose of this study was to assess the agreement between two mobile cycle ergometer systems for recording high-intensity, intermittent power output. Twelve trained male cyclists (age 31.4 +/- 9.8 years) performed a single 3 min intermittent cycle test consisting of 12 all-out efforts, separated by periods of passive recovery ranging from 5 to 15 s. Power output was recorded using a Polar S710 heart rate monitor and power sensor kit and an SRM Powercrank system for each test. The SRM used torque and angular velocity to calculate power, while the S710 used chain speed and vibration to calculate power. Significant differences (P < 0.05) in power were found at 8 of the 12 efforts. A significant difference (P = 0.001) was also found when power was averaged over all 12 intervals. Mean power was 556 +/- 102 W and 446 +/- 61 W for the SRM and S710 respectively. The S710 underestimated power by an average of 23% with random errors of */[division sign] 24% when compared with the SRM. Random errors ranged from 36% to 141% with a median of 51%. The results indicate there was little agreement between the two systems and that the Polar S710 did not provide a valid measure of power during intermittent cycling activity when compared with the SRM. Power recorded by the S710 system was influenced greatly by chain vibration and sampling rates.
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04 Mar 2013 21:45

CoachFergie wrote: I thought I would start a power meter thread to discuss the science behind this measurement tool.

I am really at a loss in trying to understand what you think the references you are posting have to do with your stated purpose in starting this thread. I guess it is all science but what do you expect the average reader to take away from what you are posting?
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04 Mar 2013 21:52

FrankDay wrote:I am really at a loss in trying to understand what you think the references you are posting have to do with your stated purpose in starting this thread. I guess it is all science but what do you expect the average reader to take away from what you are posting?


That there is scientific proof that a power meter (an SRM at least) does what it claims it does. Validly and reliably measures power. Also as a discussion point for any issues or questions people have with their power meter. For me mounting a wired SRM and for another person calibration when using Q-Rings.

Considering some people do believe that a power meter will actually make them perform better (as opposed to training, diet, recovery etc) there is clearly a need to educate people about their use.
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Rotor power cranks

04 Mar 2013 21:57

Coach,
Any opinion on the new Rotor cranks coming out that measure power. Pros, cons, is it more data than is needed etc. Thanks

rob
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04 Mar 2013 22:01

veganrob wrote:Coach,
Any opinion on the new Rotor cranks coming out that measure power. Pros, cons, is it more data than is needed etc. Thanks

rob


Nothing reported in the literature. Nor for the Power2Max model either although I did some testing with an early model and Robert Chung helped me crunch the numbers.

DC Rainmaker does some pretty excellent reviews of cycling technology if you want something to tide you over till more formal reviews are made...

http://www.dcrainmaker.com/2012/08/first-look-at-new-rotor-power-meter.html
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